Retinoid and cytokine regulation of normal breast epithelium cells (NBEC) and breast cancer cell growth and metabolism is being studied to develop new treatment strategies for the chemoprevention and treatment of breast cancer. Studies have demonstrated that NBEC are sensitive to, and are growth inhibited by, all-trans retinoic acid (AT-RA) and 9-cis retinoic acid (9C-RA) in vitro. Identification of other agents which can enhance retinoid growth inhibition and stimulation of apoptosis are in progress. NBEC have been characterized according to gene expression of the six retinoic acid receptors - RAR alpha, beta, gamma and RXR alpha, beta, gamma - by RT-PCR. Expression was correlated with growth inhibition by AT- RA and 9C-RA. To further define control of high risk mammary epithelium, an intramural clinical trial has been initiated to establish short-term mammary epithelial cell lines from women at high risk for breast cancer (including BRCA-1 positive). The growth, metabolic, and genetic properties of these cells will be examined. The effect of retinoic acid and tamoxifen on apoptosis of human breast cancer cells is being studied to define their additive/synergistic effect and to identify new targets for the treatment of breast cancer. Both AT-RA and 9C-RA act additively with hydroxytamoxifen (TAM) to inhibit growth and to stimulate apoptosis of breast cancer cells. The apoptotic regulatory gene bcl-2 is downreguated by each of these agents, and may mediate their additive effect on apoptosis. Downregulation of both gene expression and protein expression of bcl-2 has been demonstrated, suggesting an important target for gene therapy studies. These breast cancer cells secrete the negative growth factor TGFbeta, which in turn is a mediator of tamoxifen action. Studies have demonstrated that TGFbeta can replace tamoxifen, and in combination with AT-RA act additively to downregulate bcl-2 protein. TGFbeta may modulate retinoid action. A second mediator of apoptosis, Fas, is being examined. AT-RA and gamma-interferon in combination, induce Fas expression, and in combination with Fas-antibody, greatly enhance apoptosis of breast cancer cells. These observations are being developed in vitro and in vivo, and indicate a potentially important new strategy for both therapy and chemoprevention of breast cancer. The cytokine TNFalpha is a potent growth inhibitor of breast cancer cells. TNFalpha increases secretion of latent and active forms of TGFbeta, and shifts the type of isomeric secretion of TGFbeta from TGFbeta 1.2 to TGFbeta 2.2. Modulation of TGFbeta by TNF may allow a wide range of autocrine, paracrine or endocrine effects on tumor growth.